1. Field of the Invention
The invention concerns dispensers for simultaneously metering proportionate increments of extrudable materials that polymerize when mixed, while storing unused portions for later use.
2. Description of Related Art
Reliable and inexpensive dispensers are known which simultaneously meter proportionate increments of extrudable materials that polymerize when mixed together. For example, it is common to package epoxy resin and a curing agent in parallel tubes fitted with pistons that are interconnected to move together, thus simultaneously and proportionately metering increments of the resin and curing agent through closely adjacent outlets, as in U.S. Pat. Nos. 3,159,312 (van Sciver II) and 4,538,920 (Drake). Polymerizable materials that have been sold in such dispensers include adhesives, potting compounds, and molding compounds. In a dispenser shown in U.S. Pat. No. 3,323,682 (Creighton, Jr., et al.), polymerizable materials are packaged in two collapsible tubes, preferably made of plastic film, which are together fitted into a tubular cartridge to be inserted into the barrel of a typical caulking gun.
U.S. Pat. No. 2,982,396 (Shihadeh) describes a single-compartment storage container for two reactive materials that polymerize when mixed. The reactive materials are separated by a "substantially inert and impermeable barrier . . . adapted to resist the diffusion of either reactive component into the other for relatively long periods while permitting the entire contents of the one-package system including the barrier to be stirred into a substantially homogeneous and compatible mixture" (col. 1, lines 58-64). The barrier layer can be a liquid having a viscosity and density intermediate between those of the two polymerizable materials, or can be thixotropic or a gel, or can be a low-melting solid when the reaction between the two polymerizable materials is sufficiently exothermic to melt the solid barrier. Shihadeh's container is apparently designed for one-time use. In other words, it is not said to be useful for incremental (i.e., partial or repetitive) dispensing of the contents of the container.
Belgian Pat. No. 646,446 (patented Apr. 10, 1964) also concerns a container in which two or more reactive ingredients are separated by a barrier material that is said to be compatible with the reactive ingredients but neither reacts with them separately nor significantly diminishes the properties of the final product. The contents can either be mixed in the container before being extruded, or the container can be fitted with an extrusion nozzle containing a mixing element that mixes the materials when they are extruded. The Belgian patent says nothing about incremental dispensing and intervening storage of portions of the contents of the container.
Much of what is stated in the Belgian patent is repeated in U.K. Pat. Specification Nos. 1,065,560 and 1,072,272 and U.S. Pat. Nos. 3,462,008 (Tibbs '008) and 3,519,250 (Tibbs '250). None of these latter references suggests the incremental dispensing of less than the entire contents of the container at one time.
3. Other Art
While U.S. Pat. Nos. 4,098,435 and 4,221,341 (Weyn '435 and Weyn '341) do not concern materials that polymerize when mixed together, they do concern dispensers for simultaneously metering proportionate increments of extrudable materials while keeping the unused portions separated. The extrudable materials are dentifrices that are more efficacious if kept apart until they are used. However, even if contact between adjacent interactive portions of the dentifrice occurred within the dispenser, the dentrifice would nevertheless be extrudable. In contrast, even slight contact within a dispenser between two materials that polymerize when mixed could produce a skin that might clog the extrusion outlet, interfere with mixing, harm the physical properties of the polymerizate or otherwise have a deleterious effect.
A dispenser that can be used in the present invention is available from Calmar Dispensing Systems, Inc., Watchung, N.J., as the "Realex HVD" dispenser. The HVD dispenser is shown in Twin City Bottle Customer Newsletter, Vol. 1, No. 2 (April, 1986) bearing a variety of labels, including one for "All Purpose Adhesive". A Calmar advertisement in Packaging Technology, Vol. 16, No. 2 (April 1986) also shows the HVD dispenser and lists a number of potential applications. Recently the HVD dispenser has been used for "Aqua-Fresh" striped toothpaste, as shown in HAPPI, p. 74 (June, 1986).
An injection head for filling containers is shown in "Thiele Speed Nozzle", a brochure of the Thiele Engineering Company, Minneapolis, Minn.